Feed tube flame arrester

ABSTRACT

A passage for returning gases from a gasoline engine crankcase to the carburetor and for preventing flame from propagating along the tube in the direction of the crankcase consists of a brass tube having an interior strip with a width equal to the internal diameter of the tube wound into a spiral along its length and fixed within the tube. Gasses passing through the tube are thus forced into a spiral path, cooling and breaking up any flames propagating along the tube. An alternative embodiment of the feed tube is used to communicate the air side of an engine diaphragm fuel pump to the carburetor so as to dispose of fuel reaching the air side in the event of rupture of the diaphragm. The tubes are formed by tinning the elongated edges of the spiral strip with a brazing compound, inserting the strip into the tube, and heating the exterior of the tube so as to braze the edges to the interior wall.

United States Patent Polaner 1 1 June 17, 1975 FEED TUBE FLAME ARRESTER Mardy Polaner, Detroit, Mich.

Barbron Corporation, Detroit, Mich.

Filed: Aug. 13, 1973 Appl. No.1 387,906

Related US. Application Data Division of Ser. No. 177,235, Sept. 2, 1971.

Inventor:

Assignee:

u.s. c1. 123/142; 123/120; 123/121; 123/127; 123/139 AH; 123/141; 123/119 B;

I 48/180 M 1m. Cl....F02m 17/00; FO2m 25/06; F02m 29/00 Field of Search 123/119 8, 142, 139 AH. 123/120,127,121,141;4s/1s01v1 References Cited UNITED STATES PATENTS Burdon et a1 48/180 M UX Remington 123/119 B Zeibig ct a1. 123/139 AH Primary Examiner-Wendell E. Burns Attorney, Agent, or FirmKrass & Young [57] ABSTRACT A passage for returning gases from a gasoline engine crankcase to the carburetor and for preventing flame from propagating along the tube in the direction of the crankcase consists of a brass tube having an interior strip with a width equal to the internal diameter of the tube wound into a spiral along its length and fixed within the tube. Gasses passing through the tube are thus forced into a spiral path, cooling and breaking up any flames propagating along the tube.

An alternative embodiment of the feed tube is used to communicate the air side of an engine diaphragm fuel pump to the carburetor so as to dispose of fuel reaching the air side in the event of rupture of the diaphragm.

The tubes are formed by tinning the elongated edges of the spiral strip with a brazing compound, inserting the strip into the tube, and heating the exterior of the tube so as to braze the edges to the interior wall.

4 Claims, 4 Drawing Figures FEED TUBE FLAME ARRESTER This is a division of application Ser. No. 177,235, filed Sept. 2, 1971.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to flame Zlt'lttStElS for preventing the propagation of flame along a feed tube for combustible fluids, more particularly to such tubes adapted to return uncombusted gases to the carburetor of a gasoline engine, and to methods of making the same.

2. Background of the Invention In a variety of devices combustible fluids and particularly gases must be conveyed from a source such as the storage tank, to a combustion area or chamber where the gases are burned. Some form of flame arrester must be incorporated in such systems to prevent the flame from the ignited gas from backing up along the gas feed path to the source area. Such flame arresters typically operate by providing some form of tortuous path which physically breaks up the flame and dissipates its heat into the arresting element so as to cool the gas below the ignition point.

Flame arrester elements have heretofore typically taken the form of masses of metallic fibers, either woven into the form of a mesh, or unwoven, disposed in the gas feed tube. such elements tend to act as filters and may eventually clog and prevent the free flow of combustible gas. Moreover, as such fiber surfaces become coated with materials which they filter out of the combustible gas, their flame arresting action may be diminished by virture of the combustibility of these filtered materials. Accordingly, forms of flame arresters which do not tend to filter out impurities from the passing gases have been sought.

SUMMARY OF THE PRESENT INVENTION The present invention contemplates a flame arresting feed tube for combustible gases which has little tendency to collect impurities from the passed gases and does not clog up or become coated with combustible material. Moreover, the flame arrester of the present invention is extremely simple in construction, so as to be low in cost and reliable in operation, and provides excellent flame arresting action.

The present invention broadly takes the form of an elongated section of tubing having an interior longitudinally aligned baffle which gradually spirals about the central axis of the tube. The baffle is formed of an elon' gated strip of a thin metal sheet preferably having a high thermal conductivity, such as brass. The strip has a width substantially equal to the interior diameter of the tubing and its edges are fixed to diametrically opposed points on the interior of the tubing. This construction results in a pair of feed paths which spiral along the length of the tube.

Combustible gases passing through such flame arresters follow a spiral path and flow in a substantially nonlaminer manner with the strip continually being impacted by the gases and forcing them into the spiral path. This continual scouring prevents the walls from supporting any substantial buildup of dirt or grit which may be contained in the passing gases.

When the gases at the output end of the feed tube become ignited the flame passing into the tube is either divided into two separate sections. or only propagates through onehalf of the dual spiral passage through the tube. In either event the flames impact against the spiral strip which tends to diffuse their heat into the two outer walls and thereby quench the flame. If the flame only occupies one of the twin passages it is quickly cooled by the diffusion of heat into the cooler gases passing through the opposite passage. Accordingly, flame arresters formed in accordance with the present invention have proved to be highly efficient in operation.

Feed tubes formed in accordance with the present invention may be fabricated in a variety of manners, depending upon their specific configuration. For exam ple, if a feed tube having a diameter of one foot is to be constructed with a central spiral strip having a thickness at least one-half inch the edges of the center strip may be affixed to the walls of the tube by suitable screws or other fasteners passing through the exterior of the tube. However, with smaller feed tube sizes construction becomes more difficult and the present invention further contemplates a method of simply forming such tubes. The method broadly consists of tinning the longitudinal edges of the spiral wound strip before it is inserted into the outer tube by dipping the edges in a molten brazing compound. After the compound hardens the spiral strip is inserted within the tube so that its tinned edges abut the interior diameter of the tube and then the tube is heated to again melt the brazing compound and cause it to adhere between the strip edges and the tube interior. By this method tubes ofth present invention may be formed easily at a low cost.

A more specific aspect of the present invention resides in the use of such feed tubes to convey gases be tween various points on an internal combustion engine, and the carburetor intake area. Automobiles presently include feed tubes connecting the upper ends of the crankcase to the carburetor input in order to burn gases which pass the pistons and thus reduce engine emission and increase the fuel economy of the engine. The formation of a section of this return tubing as a hollow tube with a spiral interior baffle strip has been found to completely eliminate the possibility of engine damage due to backfire under operating engine conditions and to eliminate the need for valves which have been heretofore used to prevent flame propagation which continually tend to clog.

Another specific aspect of the present invention resides in the use of a feed tube having an interior spiral baffle to connect the air side of a diaphragm type fuel pump to the carburetor intake. Present diaphragm fuel pumps are vented to atmosphere so as to avoid pressure variations when the diaphragm flexes to modify the fuel compartment volume. In the event of rupture of the diaphragm gasoline will collect on the air side and the fumes will pass out of the vent and produce a potentially dangerous condition. The present invention contemplates connecting the fuel pump vent to the input side ofthe carburetor through a passage which includes a spiral baffle flame arrester. In the event of fuel pump diaphragm rupture the vaporized gases will pass to the carburetor. At the carburetor. the baffle strip is carried beyond the end of the feed tube and bent downwardly in the direction of the carburetor. Gases passing out will tend to be condensed on the strip by the cool input air and drip into the carburetor. This may cause an overrich fuel mixture and a resultant rough engine operation, but this condition will serve as a warning to the driver that the engine is not operating properly. In any event the potentially dangerous fumes are safely contained within the engine system.

Other objectives. advantages and applications of the present invention will be made apparent by the following detailed description of two preferred embodiments of the invention. The description makes reference to the accompanying drawings, in which:

FIG. I is a view of a feed tube flame arrester formed in accordance with the present invention with sections broken away to better illustrate the interior spiral;

FIG. 2 is a sectional view through an air intake associated with a carburetor of an internal combustion en gine to which uncombusted gases are fed through a feed tube system formed in accordance with the present invention;

FIG. 3 is a front view of an engine incorporating a return for uncombusted crankcase gases in accordance with the present invention; and

FIG. 4 is an illustration of an alternative embodiment of the invention similar to FIG. 3 except that the air side of a diaphragm fuel pump is the source of the uncombusted gases sent to the carburetor.

Referring to FIG. I, a feed tube flame arrester formed in accordance with the preferred embodiment of the present invention utilizes a section of tubing 10 which is circular in cross section. The tubing is preferably formed of a metal having good thermal conductivity such as brass and in a typical application in connection with an internal combustion engine may have an outer diameter of 0.250 inches and a wall thickness of 0.032 inches. When used in connection with the feeding of rather dilute combustible gases such as gases from the engine crankcase. a length of tube of approximately 3 inches has been determined to be sufficient to prevent the passage of flame.

The tubing section 10 has a bulge 12 adjacent one end. which will be termed as input end. so that a suitable hose may be inserted over the tube and coupled thereto with a standard hose coupling member.

An interior flame arresting baffle 14 is formed of an elongated strip ofa thermally conductive metal such as brass which may have a developed length slightly in excess of the length of the tube section 10. The strip 14 has a width substantially equal to the interior diameter of the tube 10. The strip 14 is spiralled about its longitudinal axis so that it makes a 180 turn in slightly less than 1 inch.

The strip 14 is disposed within the tube 10 with its edges in abutment with the sidewalls so as to effectively form a pair of spiral parallel separated passages through the tube. One end of the strip is flush with the end of the tube 10 adjacent to the bulge l2, and the strip 14 projects beyond the other end of the tube 10 and is bent at right angles thereto so as to form a tongue 16.

To fix the strip 14 within the tube the edges of the strip are passed through a molten solder solution before insertion within the tube. Ifthe brass is fully cleaned no fluxing is required, but otherwise a good adhesion of the solder to the edges may be achieved by using a suit able commercially available flux for the solder. After the solder has solidified the strip 14 may be manually inserted into the tube. The interior of the tube may be brushed with an appropriate flux to obtain good adhesionv The tube may then be heated from the outer side. preferably in an induction furnace. above the melting point of the solder. so as to again melt the solder. After cooling the edges ofthe strip will be bonded to the inte rior of the tube at both edges.

FIG. 2 illustrates the manner in which the tube 10 may be connected to the air intake, generally indicated at 18, of an internal combustion engine carburetor system. The air intake may either take the form of an air cleaner, as is employed on automobiles and most land vehicles, or a flame arrester of the type used on marine engines. Both devices are generally similar with the exception of the nature of the materials through which the intake is passed.

The intake unit l8 includes a cylindrical metal top cover 20 and an annular lower ring 22. The unit is supported on the horn 24 of a carburetor. An appropriate cylindrical flame arrester or filter element 26 is supported between the down-turned edges of the top 20 and the lower annular ring 22. The element 26 is illustrated as having a thickness typical of that of a marine flame arrester. If the unit 18 were to act as a filter, a relatively thicker element would be employed. Air passes into the carburetor through the element 26 in the manner illustrated by the arrow to the right of FIG. 3.

The feed tube 10 is bent adjacent to its middle as at 30, so as to form two parallel. nonlinear sections. The tube passes through a hole 32 formed in the element 26 just below the downturned edge of the top 20, and the upper edge of the tube is brazed to the bottom edge of the top 20 at 34, so that the tube projects radially inwardly toward the center of the air intake unit 18. The tongue 16 projects downwardly toward the carburetor 24. A rubber feed tube 36 connects to the input end of the tube 10 with a suitable hose clamp 38 retaining the tube 36 about the bulge 12.

FIG. 3 illustrates the feed tube as incorporated in an internal combustion engine to return crankcase gases to the carburetor. The engine, generally indicated at 40, includes a crankcase 42 and a carburetor 44. The air intake unit 18 is mounted on top of the carburetor and the input end of the tube 10 is connected to a port 46 in the top of the crankcase 42 by the tubing 36. In this manner the combustible gases in the crankcase tend to rise through the tube 36 and pass into the air intake 18 through the tube 10. The gases tend to con dense on the tongue 16 because of the cool air going through the intake unit and then either evaporate or drip into the carburetor. If the carburetor tends to backfire into the intake area, as sometimes happens, any flame reaching the output of the tube 10 will be forced to follow a spiral path between the sides of the strip 14 and the interior diameter of the tube 10 and its temperature will quickly be lowered by the dissipation of the heat through the strip and the tube to the point where the flame is quenched. The flame will normally be quenched in one of the two spiral paths before the other and the induction of heat into the relatively cool intake gas will quickly quench the flame in the other spiral path.

FIGv 4 illustrates a diaphragm type fuel pump, generally indicated at 50, having a chamber 52 supplied by an input line 54 and an output line 56. The upper or air side of the diaphragm 50 is vented by a feed line 36 which connects to a carburetor intake in the same manner as the apparatus of FIG. 2. This achieves venting of the air side of the fuel pump. Additionally. if gasoline collects in the air side by virtue of rupture of the diaphragm. gasoline vapor does not feed into the engine compartment but is rather returned to the carburetor through the tube 36 in the feed tube 10.

The exact configuration of the flame arrester in terms of the material and dimensions of the tube and the strip will be a function of the gas dynamics. For a relatively large diameter it will be necessary to have a relatively tight spiral configuration so as to force a flame against the strip surfaces.

Having thus described my invention, 1 claim:

1. In a combustion engine having a carburetor for mixing air with fuel, a feed line for conveying combustible gases from a source to the carburetor including an elongated section of closed tube having one open end connected directly to the source and the other end connected to the carburetor so as to pass undiluted gases from the source directly to the carburetor. said tube having an interior flame arresting baffle formed of an elongated strip twisted about its elongated axis and having both of its longitudinal edges fixed to the interior of the tube so that the longitudinal axis of the strip coincides with the longitudinal axis of the tube and having one end terminating at the carburetor end of the tube.

2. The engine of claim 1 wherein the source of combustible gases consists of the engine crankcase.

3. The engine of claim 1 wherein the source of combustible gases consists of the air side of a diaphragm type fuel pump for said engine.

4. The feed line of claim 1 wherein said elongated strip extends beyond the end of the tube at the carburetor. 

1. In a combustion engine having a carburetor for mixing air with fuel, a feed line for conveying combustible gases from a source to the carburetor including an elongated section of closed tube having one open end connected directly to the source and the other end connected to the carburetor so as to pass undiluted gases from the source directly to the carburetor, said tube having an interior flame arresting baffle formed of an elongated strip twisted about its elongated axis and having both of its longitudinal edges fixed to the interior of the tube so that the longitudinal axis of the strip coincides with the longitudinal axis of the tube and having one end terminating at the carburetor end of the tube.
 2. The engine of claim 1 wherein the source of combustible gases consists of the engine crankcase.
 3. The engine of claim 1 wherein the source of combustible gases consists of the air side of a diaphragm type fuel pump for said engine.
 4. The feed line of claim 1 wherein said elongated strip extends beyond the end of the tube at the carburetor. 